Field of the Invention
The present invention relates to blood pressure information measurement device cuffs that are used while being worn on a measurement area when measuring blood pressure information such as a blood pressure value, and to blood pressure information measurement devices provided with such cuffs.
Description of the Background Art
Blood pressure information measurement devices obtain blood pressure information of a measurement subject. The blood pressure information obtained by such blood pressure information measurement devices includes various types of information related to the circulatory system, such as a systolic blood pressure value (a maximum blood pressure value), a diastolic blood pressure value (a minimum blood pressure value), an average blood pressure value, a sphygmogram, pulse, AI (Augmentation Index) value, and the like of the measurement subject, and so on. Stress on the heart, changes in the hardness of arteries, or the like can be understood based on this blood pressure information. A blood pressure information measurement device is used in the early discovery, prevention, treatment, and so on of circulatory system conditions.
Generally speaking, a blood pressure information measurement device cuff (called simply a “cuff” hereinafter) is used in the measurement of blood pressure information. Such a cuff has a bladder-shaped cover member, formed having a band shape, that has an internal cavity, and a fluid bladder for applying pressure to a body (an artery) is contained within the bladder-shaped cover member. The cuff is wrapped around a part of the body, such as the upper arm.
In a blood pressure information measurement device used to measure blood pressure values such as a systolic blood pressure value or a diastolic blood pressure value (called simply a “sphygmomanometer” hereinafter), the cuff is wrapped around the surface of part of the body. A fluid such as air, a liquid, or the like is injected into or exhausted from the fluid bladder enclosed within the cuff. The fluid bladder is inflated by injecting a fluid into the fluid bladder. On the other hand, the fluid bladder is deflated by exhausting the fluid from the fluid bladder. Changes in the pressure within the fluid bladder produced when the fluid bladder inflates or deflates are registered as an arterial sphygmogram or a blood pressure value.
Generally speaking, measuring blood pressure through a non-invasive blood pressure measurement method involves wrapping the cuff around the upper arm, increasing the air pressure within the cuff in order to stop the flow of blood, and pressurizing the artery. At this time, it is extremely important to adjust the tightness caused by friction produced between the air bladder and other internal components such as the bladder-shaped cover member, ensure that the tightness of the cuff does not decrease during measurement, and align the center position of the air bladder directly above the artery.
There are devices that include a curler, configured of an approximately cylindrical, flexible member that guides the cuff along the upper arm, in order to facilitate the tightening of the cuff so as to follow the upper arm. JP-H2-1221A (Patent Literature 1) and JP-H6-38931A (Patent Literature 2) can be given as disclosures of such a cuff.
When pressure is applied to the upper arm using an air bladder, if, for example, the air bladder is inflated in an approximately cylindrical shape while wrapped loosely upon the measurement subject, there are cases where the volume of the air within the cuff will become more than ten times greater the volume within the blood vessels. In such a case, the measured blood pressure value will be a measurement result that contains more error than a normal blood pressure measurement value.
FIG. 13 is a schematic diagram illustrating a cross-section of an upper arm 301. The upper arm 301 contains a bone 302, and an artery 303 is located at a position closer to the subject's body from a top position (L2) of the upper arm 301. FIG. 14 is a cross-sectional schematic diagram illustrating a state in which a cuff has been properly affixed to the upper arm. The center position of an air bladder 361 is positioned directly above the artery 303, and the air bladder 361 is suitably biased toward a measurement area by a curler 391. Note that in FIG. 14, a bladder-shaped cover member configured as a band, which houses the air bladder 361 and the curler 391, is not shown. The same applies to FIG. 15.
FIG. 15 is a cross-sectional schematic diagram illustrating a state in which the cuff has been wrapped around the upper arm loosely. Although the center position of the air bladder 361 is located directly above the artery 303, there is a large distance between the curler 391 and the upper arm 301 (that is, a distance R2 is longer than a distance R1 shown in FIG. 14), which causes an increase in the volume of the air bladder 361 (that is, an expansion of the air volume within the cuff), resulting in a state where the artery 303 cannot be sufficiently pressurized. As a result, the measured blood pressure value will be a measurement result that contains more error than a normal blood pressure measurement value.